Dynamiczne budowanie UI zależne od uprawnień użytkownika

  1:  private void Form1_Load(object sender, EventArgs e)
  2:  {
  3:  	btnAddUser.Visible = Thread.CurrentPrincipal.IsInRole("can add user");
  4:  	btnShowPosts.Visible = Thread.CurrentPrincipal.IsInRole("can show posts");
  5:  	//...
  6:  	//...
  7:  	//...
  8:  	//...
  9:  
 10:  }

  1:  [AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = false)]
  2:  public sealed class UserOperationAttribute : Attribute
  3:  {
  4:  	private readonly string[] _requiredPrivileges;
  5:  	public readonly string DisplayName;
  6:  
  7:  	public UserOperationAttribute(string displayName, params string[] requiredPrivileges)
  8:  	{
  9:  		_requiredPrivileges = requiredPrivileges;
 10:  		DisplayName = displayName;
 11:  	}
 12:  
 13:  	public bool IsSatisfied
 14:  	{
 15:  		get
 16:  		{
 17:  			// current user has all required privileges
 18:  			return _requiredPrivileges.All(Thread.CurrentPrincipal.IsInRole);
 19:  		}
 20:  	}
 21:  }

  1:  public class UserOperationDiscovery
  2:  {
  3:  	public static Dictionary<Type, UserOperationAttribute> Perform()
  4:  	{
  5:  		var actions = from type in AppDomain.CurrentDomain.GetAssemblies().SelectMany(x => x.GetTypes())
  6:  					  let actionAttribute = type.GetCustomAttributes(typeof(UserOperationAttribute), false)
  7:  						.Cast<UserOperationAttribute>().SingleOrDefault()
  8:  					  where actionAttribute != null && actionAttribute.IsSatisfied
  9:  					  select new { type, attr = actionAttribute };
 10:  
 11:  		return actions.ToDictionary(x => x.type, x => x.attr);
 12:  	}
 13:  }

  1:  private void LoadOperations()
  2:  {
  3:  	var operations = UserOperationDiscovery.Perform();
  4:  	operations.ToList().ForEach(
  5:  		o =>
  6:  		{
  7:  			// new button for each operation
  8:  			Button btn = new Button
  9:  			{
 10:  				Text = o.Value.DisplayName,
 11:  				Dock = DockStyle.Fill,
 12:  				Tag = o.Key
 13:  			};
 14:  
 15:  			btn.Click += (s, e) =>
 16:  			{
 17:  				// dispose of currently displayed operation
 18:  				if (Placeholder.Controls.Count > 0)
 19:  					Placeholder.Controls[0].Dispose();
 20:  				Placeholder.Controls.Clear();
 21:  
 22:  				// create new instance of operation on each click
 23:  				var newControl = (Control)Activator.CreateInstance((Type)btn.Tag);
 24:  				newControl.Dock = DockStyle.Fill;
 25:  				Placeholder.Controls.Add(newControl);
 26:  			};
 27:  
 28:  			this.buttonsPanel.Controls.Add(btn);
 29:  		});
 30:  }